[Thales454]

Hi, I'm just looking for a few words from anyone who have already used a 1.7x TC with a DA* 60-250. How does the TC affects your AF and paperture? I would like to reach 200~400mm with a decent IQ (e.g. Sigma 100-300) which takes flawless pictures even with a 1.4x TC, but I find the 60mm low end extremly useful in the DA*, so I'm here to ask if would the DA* work so well with a TC as Sigma, or if perhaps, I'm better off without it. I've read somewhere that the DA* doesn't seems to work very well with a TC (or perhaps that user had some issues with his TC...).

I would also like to take advantage of this topic to ask if you could rather from 1 to 100, how often do you take pictures within the 60~90mm range? (Because that's the gap I will have with my Tamron 17-50 in case I end up with the 100-300) Because I'm not rating that gap as a ''must fill'' atm.

I'm also not taking in account prime lenses due to the fact that I'm a traveler and can't compromise that much weight carrying many lenses.

I'm also having a debate about my gear in here:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/142686-packing...ml#post1489885

Updated:

Making this plain and simple: Will the IQ degradation of a DA* 60-250 + 1.7x TC be worth the 60~90mm range coverage?

If not, my answer is the 100-300, which I know it's going to feed my needs =)

Thanks for your time in advance! =D

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Last edited by Thales454; 05-09-2011 at 11:13 AM.

[twitch]

Given the DA70 and the DA*50-135 are 2 of my most used lenses I'd have to say I can't imagine not having that range covered. Nor would I want to pull out a beast like a 100-300 to snap a few portraits of the kids.

If you buy the 100-300 you could buy a DA70 to fill the gap, it hardly weighs anything, probably less than just the hood of the 100-300, LOL.

To be honest the 100-300 doesn't seem like a good choice for travelling, but I guess you have reasons...

[Thales454]

But I guess you have reasons...

Birds indeed =D and other different animals that I can't get close from, when doing some field trips, like monkeys or so. A user suggested me to crop 17-50's image in case I need to cover that range, once in a while, which I found to be useful since it's pretty sharp. Because I'll be using 100-300 at wide open places, so whenever I'm inside things like museums it won't require more than the 17-50

100-300 actually weights twice as much as DA* 50-135, however I will never reach that given 200~400mm range that I've mentioned, which would require me another lens and more money :x

But sure, thanks for your insight. =D

[SOldBear]

The best TC to work with DA* zoom lens is the Pentax 1.7X AFA. You focus the lens approximately, then half press the shutter release button for the AFA to take over focusing. The AFA modifies the aperture of the lens to the correct value (e.g. the camera will show the AFA + the 60-250mm F/4 combo to have the max. aperture of F/6.7). But the AFA blocks the focal length info from the lens to the camera. In other words, the camera will ask you for the focal length if SR is on.

The Tamron 1.4X TC will autofocus with the DA* zoom lens at the short local end of the FL range (but there's no reason to us a TC with a zoom lens set at the short end of the range). At the long end, AF will hunt back and forth as if it can't decide where/whether to lock focus. If if release the half press, and half press again, there is a chance that it will lock autofocus. But oftentimes, the opportunity is gone. The focal length and the aperture data will be transferred as is from the lens to the camera. The camera doesn't know the TC is between it and the lens.

The Tamron 2X TC will behave similarly to the Tamron 1.4X TC with one exception: the 2X TC does NOT autofocus at all.

I don't think the Tamron TCs I tried were defective. I tried at least 2 copies of each. The symptoms were the same.

[Digitalis]

it is important to note the Sigma 100-300mm f/4 APO EX DG is an IF lens design - internal focusing and internal zooming - it stays the same length regardless of focus/zoom setting - the Pentax DA*60-250mm f/4 SDM WR does change physical length when zooming/focusing. In fact, with the lens hoods on the DA*60-250 f/4 is longer than the Sigma 100-300mm f/4 APO EX DG at the longest zoom setting.

[Thales454]

The Tamron 1.4X TC will autofocus with the DA* zoom lens at the short local end of the FL range. At the long end, AF will hunt back and forth as if it can't decide where/whether to lock focus.

So the 1.7x hunts less than the 1.4x (at long end) with DA* series?

[SOldBear]

So the 1.7x hunts less than the 1.4x (at long end) with DA* series?

AF with the 1.7X AFA is somewhat slow. "Slow" is a relative term, and is expected at max aperture of F/6.7.

But the hunting of the 1.4X + DA* zoom combo is painful...

[dgaies]

So the 1.7x hunts less than the 1.4x (at long end) with DA* series?

AF with the 1.7X AFA is somewhat slow. "Slow" is a relative term, and is expected at max aperture of F/6.7.

But the hunting of the 1.4X + DA* zoom combo is painful...

I would say the focus speed with the 1.7x AF-A is actually pretty decent, all things considered. Keep in mind you have to prefocus manually, so perhaps if you take that into account the overall speed of the focusing is so-so.

But as SOldBear said, autofocusing with the Tamron 1.4x can be painful. Even though you don't have to, you'd get much better results prefocusing close with the 1.4x as well. Otherwise, it can be quite painful and frustrating. The bottom line is there just really isn't a TC that works particularlly well with SDM lenses at the moment.

[Thales454]

The bottom line is there just really isn't a TC that works particularlly well with SDM lenses at the moment.

I see... So what if I only focus manually, how would you compare the overall IQ of a DA* 60-250 + 1.7TC vs 100-300 + 1.4x TC?

My real bottom line is to discover if that IQ degradation will compensate the 60~90 coverage.

[dgaies]

I see... So what if I only focus manually, how would you compare the overall IQ of a DA* 60-250 + 1.7TC vs 100-300 + 1.4x TC?

My real bottom line is to discover if that IQ degradation will compensate the 60~90 coverage.

Although I've owned both TCs and both lenses, I never did any specific testings to try and determine which had the least amount of IQ degredation. That said, my gut feeling is that if IQ at the long end is your prioirtiy, then regardless of which TC you stick on, the 100-300 might be your better overall option. You then have the option of buying a "matching" Sigma 1.4x for it, which you should be able to find for about $100-125 (used).

[Thales454]

That said, my gut feeling is that if IQ at the long end is your prioirtiy, then regardless of which TC you stick on, the 100-300 might be your better overall option.

Yes it is, as I actually believe I will barely need to use the 60~90mm range

Thanks for your insight! =D

[dgaies]

Yes it is, as I actually believe I will barely need to use the 60~90mm range

Thanks for your insight! =D

You're welcome. For me personally when I tried both 100-300 and 60-250 to last year, I ended up choosing the 60-250 primarily for extra 60-100mm range. I found that I was using the lens on the wide end about as much as the long end, so for me it made sense to keep the 60-250. But I was mostly shooting my son playing soccer, and didn't really need much reach beyond 250mm on the long end.

[normhead]

Looking at photozone comparisons, I'd say at 200mm the 60-250 is the better lens although you can't do a direct comparison. Both have 2 fields excellent and 2 very good at 200mm, but the 60-250's are further up in the excellent.

Another thought might be the difference between 300 and 250.. is it really different? When I go from 200 to 250 on my 60-250, I don't notice much difference.

The 100-300 is also very good. It's numbers aren't as high up in the excellent range as the DA*60-250, but no one knows what those numbers mean, it's tested on a different camera body.

But, you can get a functional TC for the Sigma. For me that would be the deciding factor if I were starting from scratch. The sigma can be made to functionally reach 500mm. At this point, I'd kill for that.

[Thales454]

Both have 2 fields excellent and 2 very good at 200mm, but the 60-250's are further up in the excellent.

Without a TC, the 60-250 is without any doubts the best lens when it comes to IQ. However 250x1.4TC = 350mm, 250x1.7TC = 425mm, 300x1.4TC = 420mm.

So my thought are that a 100-300 + 1.4x TC will have a better IQ than a 60-250 + 1.7x TC, which I believe you will agree. =D

[bymy141]

Another thought might be the difference between 300 and 250.. is it really different? When I go from 200 to 250 on my 60-250, I don't notice much difference.

This is more true than you realise.
The difference between 250mm and 300mm is not that much at all.
Try playing with the Tamron lens selection tool.
I can realy recommend it!

The link is here: Focal length comparison tool, Tamron USA

It is IMHO a very good tool.

It showed me that I need >400mm to make a difference over my DA*60-250mm, 300mm is just not enouhj....

Happy shooting, Bert